Heat-resistant self-repairing zinc silicate anticorrosive paint and preparation method thereof

Abstract

The invention belongs to the field of metal corrosion and protection, and particularly relates to a heat-resistant self-repairing zinc silicate anticorrosive coating and a preparation method thereof. The coating comprises a component A and a component B in a mass ratio of 100: 43, the component A comprises ethanol, xylene, a rheological additive, zinc powder and a filler; the component B comprises tetraethoxysilane, a hydrochloric acid solution, absolute ethyl alcohol and a solvent; the filler is a composition of two or more of low-melting-point glass powder, zinc oxide powder, conductive mica powder and lamellar graphene powder. The coating has an environment response type protection structure through new filler components and size adjustment, so that the high temperature resistance of the zinc silicate coating, the adhesive force after heat influence and the anti-corrosion self-repairing performance are improved.

Description

Technical Field

[0001] The present invention belongs to the field of metal corrosion and protection, and particularly relates to a heat-resistant self-healing zinc silicate anti-corrosion coating and a preparation method thereof. Background Art

[0002] In the fields of petrochemical industry, shipbuilding and metallurgy, the corrosion protection of steel materials cut and welded in workshops and high-temperature pipelines has always been a technical difficulty. Zinc silicate coatings are widely used due to their excellent initial rust prevention performance and good electrical conductivity, and zinc silicate-based coatings have become the mainstream choice for shop primer and high-temperature pipeline primer due to their heat resistance (usually tolerating 300-400 °C). However, when serving in an environment of high-temperature - normal-temperature cyclic thermal shock, corrosion medium penetration and mechanical stress coupling for a long time, traditional zinc silicate coatings expose significant technical defects. In repeated thermal cycles (such as pipeline start-stop and multiple welding and cutting conditions), due to the difference in thermal expansion coefficients between the coating binder and inorganic zinc powder, micron-sized cracks and pores are likely to occur in the zinc silicate coating. CN119592213A mentions that existing anti-corrosion coatings cannot meet the application requirements when the temperature exceeds 550 °C, and for the zinc powder in the zinc silicate coating, a large number of voids will be generated in-situ in the coating when the temperature exceeds its melting point, further limiting its application at higher temperatures.

[0003] Limitations of passive protection. Current improvement schemes mainly focus on improving the heat resistance of fillers (such as introducing phosphorus iron powder / ferrotitanium powder fillers) or adding high-temperature secondary film-forming fillers (such as low-melting glass powder). Although the former improves the heat resistance of the coating, the cathodic protection effect of the coating decreases significantly; although the latter improves the thermal shock resistance of the coating, the porosity of the coating is relatively high due to the in-situ pores generated by the molten fillers at high temperatures (Patent CN117736592A and the journal paper "Influence mechanism of added low-melting glass powder on the properties of high-temperature organic composite coatings", Ceramics International).

[0004] Poor adaptability of self-healing technology. Existing self-healing coatings mostly rely on microcapsule-coated corrosion inhibitors (such as isocyanate) or shape memory polymers (Patent CN119161776A). However, in high-temperature scenarios, microcapsules are prone to premature rupture (thermal decomposition at >250 °C) or the repair agent fails at high temperatures, and the inorganic silicate system is difficult to be compatible with organic repair components.

[0005] In the traditional zinc silicate coating under the coupled environment of high-temperature thermal shock and corrosion, irreversible expansion of microcracks is caused by thermal stress mismatch, and there is a lack of an active repair mechanism, severely restricting its long-term protection ability. This patent breaks through the bottleneck of the existing technology and proposes a heat-resistant and corrosion self-repair strategy based on dynamic response and structural reconstruction: through the secondary film-forming technology of micro-nano fillers, dynamic filling of micro-defects and interfacial chemical bonding are realized at the crack interface caused by thermal shock; in the corrosion environment, a composite of zinc-based and lamellar conductive fillers is introduced, and a dense composite passivation film is in-situ generated at the defect interface through cathodic protection to block the penetration path of the corrosion medium. This technology enables the coating to have crack self-healing ability in both high-temperature / room-temperature corrosion environments and structural stability across temperature ranges, solving the core contradiction that it is difficult to be compatible between the repair function and heat resistance performance in the traditional solution. Summary of the Invention

[0006] Aiming at the problems of poor heat resistance performance of the anti-corrosion primer in the existing technology and the reduction of adhesion and anti-corrosion performance after being affected by high temperature, the present invention provides a heat-resistant self-repairing anti-corrosion primer, which improves the high-temperature resistance performance, adhesion and anti-corrosion performance after being affected by heat through new filler components and size structures.

[0007] The technical solution of the present invention is as follows: A heat-resistant self-repairing zinc silicate anti-corrosion coating, characterized in that the coating comprises component A and component B with a mass ratio of 100:43; calculated by mass parts, component A comprises 15 parts of ethanol, 20 parts of xylene, 5 parts of rheological aid, 40 - 45 parts of zinc powder and 15 - 20 parts of filler; component B comprises 35 - 45 parts of tetraethyl orthosilicate, 0.3 - 0.6 parts of hydrochloric acid solution, 54.4 - 64.7 parts of absolute ethanol; the coating has an environment-responsive protection structure. The filler is a composition of two or more of low-melting-point glass powder, zinc oxide powder, conductive mica powder, and lamellar graphene powder. The environment-responsive protection structure includes a secondary film-forming - microporous structure of the coating in a high-temperature environment and a self-repairing dense structure in a room-temperature corrosion environment.

[0008] Further, for the above-mentioned heat-resistant self-repairing zinc silicate anti-corrosion coating, the particle size of the zinc powder is 2000 - 800 mesh, the particle size of the low-melting-point glass powder is 5000 - 3000 mesh, the particle size of the zinc oxide powder is 500 nm - 1 μm, the conductive mica is 1250 mesh, and the diameter of the lamellar graphene powder is 10 μm.

[0009] Further, for the above-mentioned heat-resistant self-repairing zinc silicate anti-corrosion coating, the low-melting-point glass powder is a micro-nano scale filler processed by a ball milling process for the second time. This is because large-sized low-melting-point glass powder will leave large in-situ holes after melting, and reducing its particle size can effectively improve the infiltration effect and the density of the coating.

[0010] Furthermore, for the above-mentioned heat-resistant self-healing zinc silicate anticorrosive coating, the concentration of the hydrochloric acid solution is 0.3 - 1 mol / L, and the tetraethyl orthosilicate is a tetraethyl orthosilicate polymer with a molecular weight of 40%.

[0011] Furthermore, for the above-mentioned heat-resistant self-healing zinc silicate anticorrosive coating, the rheology aid is selected from one or a mixture of fumed silica, organic bentonite, and polyvinyl butyral.

[0012] The preparation method of the above-mentioned heat-resistant self-healing zinc silicate anticorrosive coating includes the following steps: Step 1: Prepare Component A: Mix ethanol and xylene, add the rheology aid under stirring, add the filler after uniform dispersion, stir for 10 - 20 min and then transfer to a sand mill for grinding. After the grinding is completed, transfer the grinding slurry to a dispersion tank; slowly add zinc powder and disperse and mix on the dispersion tank for 30 min. After the fineness of the slurry reaches 50 μm, Component A is obtained; Step 2: Prepare Component B: Mix tetraethyl orthosilicate and absolute ethanol, and slowly drop the hydrochloric acid solution into the mixture at a stirring speed of 300 - 400 r / min, and finish dropping within 20 - 30 min. Continuously stir for 50 - 70 min for hydrolysis reaction, and then add absolute ethanol for dilution to obtain the formulated Component B; Step 3: Mix Component A and Component B evenly according to a mass ratio of 100:43 to obtain the heat-resistant self-healing anticorrosive coating.

[0013] Furthermore, for the preparation method of the above-mentioned heat-resistant self-healing zinc silicate anticorrosive coating, when adding the filler in Step 1, if the filler added is lamellar graphene, the dispersing aid sodium dodecyl sulfate needs to be added to the ethanol solution, and the addition amount is 5% of the mass of graphene, and ultrasonically disperse for 10 min.

[0014] Furthermore, for the preparation method of the above-mentioned heat-resistant self-healing zinc silicate anticorrosive coating, when adding the filler in Step 1, if the filler added is conductive mica powder, the conductive mica powder needs to be surface-modified with a titanate coupling agent, diluted with a solvent, stirred, ultrasonically treated, filtered, and dried before use.

[0015] Furthermore, for the preparation method of the above-mentioned heat-resistant self-healing zinc silicate anticorrosive coating, the heat-resistant self-healing anticorrosive coating obtained by mixing evenly in Step 3 is diluted with 0 - 10% of the coating mass of ethanol and then sprayed on the steel plate to form a dense heat-shock-resistant anticorrosive inorganic zinc silicate coating.

[0016] Furthermore, in the preparation method of the above heat-resistant self-healing zinc silicate anti-corrosion coating, the heat-shock-resistant anti-corrosion inorganic zinc silicate coating has cathodic protection characteristics before and after thermal shock, has the function of self-healing coating defects, and after thermal shock, the cohesive force of the coating and the coating-substrate bonding force will both be improved, forming a porous coating structure to improve the cathodic protection effect of the coating.

[0017] Advantages and beneficial effects of the present invention: 1. The present invention uses micro / nano-scale low-melting glass powder as the functional phase, triggers a secondary film-forming effect at a high temperature of 600 °C, and realizes in-situ self-healing of coating micro-cracks through melting and flowing, significantly improving the thermal shock stability of the coating. After thermal shock, the coating does not peel or flake, and the coating adhesion is increased to 4.91 Mpa at most; 2. The present invention introduces conductive mica powder or graphene powder to increase the effective zinc content in the coating at the micro / nano scale, hinders the melting and agglomeration of zinc powder in a high-temperature environment, and increases the cathodic protection period of the coating to 6 days at most. The coating has the function of self-healing defects in a corrosive environment, and solves the problem of corrosion resistance degradation caused by thermal shock at 600 °C; 3. Based on the multi-scale filler compounding theory, the present invention provides a design with self-healing ability for defects in both high-temperature / room-temperature corrosion environments and structural stability across temperature ranges, and provides a solution to the technical problem that self-healing function and heat-resistant anti-corrosion performance are difficult to be compatible. Description of the drawings

[0018] Figure 1 It is a schematic diagram of the structural changes of the modified coating and the traditional coating at 600 °C; Figure 2 It is a cross-sectional BSE diagram of the modified coating in Example 3 after being immersed in a 3.5% salt water solution for 168 hours. Specific embodiments

[0019] Next, the specific embodiments of the present invention will be further described in detail with reference to the accompanying drawings of the specification and examples. The following examples are used for the description of the present invention, but cannot be used to limit the scope of the present invention.

[0020] Example 1

[0021] A heat-resistant self-healing zinc silicate anti-corrosion coating in this example contains component A and component B with a mass ratio of 100:43; by mass, component A includes 15 parts of ethanol, 20 parts of xylene, 5 parts of rheological aid, 45 parts of zinc powder and 15 parts of filler; component B includes 35 parts of tetraethyl orthosilicate, 0.3 parts of hydrochloric acid solution, and 64.7 parts of absolute ethanol; The filler is a composition of low-melting glass powder and zinc oxide powder with a mass ratio of 1:2; the particle size of the zinc powder is 2000 mesh; the particle size of the low-melting glass powder is 5000 mesh, and the low-melting glass powder is a micro-nano scale filler processed by ball milling twice; the tetraethyl orthosilicate is a tetraethyl silicate polymer with a molecular weight of 40%; the concentration of the hydrochloric acid solution is 0.3 mol / L; the rheological aid is organobentonite and polyvinyl butyral.

[0022] The specific preparation method is as follows: Step 1. Prepare Component A: Mix ethanol and xylene, add the rheological aid under stirring, add the filler after uniform dispersion, transfer to a sand mill for grinding after stirring for 10 min, and transfer the ground slurry to a dispersion tank after grinding; slowly add zinc powder, and disperse and mix on the dispersion tank for 30 min. After the fineness of the slurry reaches 50 μm, Component A is obtained; Step 2. Prepare Component B: Mix tetraethyl orthosilicate and absolute ethanol, slowly drop the hydrochloric acid solution into the mixture at a stirring speed of 300 r / min, and finish dropping within 20 min. Continuously stir for 50 min for hydrolysis reaction, and then add absolute ethanol for dilution to obtain Formulation Component B; Step 3. Mix Component A and Component B evenly according to a mass ratio of 100:43 to obtain a heat-resistant self-healing anticorrosive coating.

[0023] Spray the heat-resistant self-healing anticorrosive coating obtained by mixing evenly in Step 3 onto the steel plate according to the coating mass to form a dense heat-resistant impact anticorrosive zinc silicate coating.

[0024] Example 2

[0025] A heat-resistant self-healing zinc silicate anticorrosive coating in this example contains Component A and Component B with a mass ratio of 100:43; by mass fraction, Component A includes 15 parts of ethanol, 20 parts of xylene, 5 parts of rheological aid, 40 parts of zinc powder, and 20 parts of filler; Component B includes 45 parts of tetraethyl orthosilicate, 0.6 parts of hydrochloric acid solution, and 54.4 parts of absolute ethanol; The filler is a composition of low-melting glass powder, zinc oxide powder, and conductive mica powder with a mass ratio of 1:2:1; the particle size of the zinc powder is 800 mesh; the particle size of the low-melting glass powder is 3000 mesh, and the low-melting glass powder is a micro-nano scale filler processed by ball milling twice; the particle size of zinc oxide powder is 500 nm, and the particle size of conductive mica is 1250 mesh. It needs to be surface-modified with a titanate coupling agent, diluted with a solvent, stirred, ultrasonicated, filtered, and dried before use. The tetraethyl orthosilicate is a tetraethyl silicate polymer with a molecular weight of 40%; the concentration of the hydrochloric acid solution is 1 mol / L; the rheological aid is fumed silica.

[0026] The specific preparation method is as follows: Step 1. Prepare Component A: Mix ethanol and xylene, add a rheology aid under stirring, add a filler after uniform dispersion, transfer to a sand mill for grinding after stirring for 20 min, and transfer the ground slurry to a dispersion tank after grinding; slowly add zinc powder, and disperse and mix on the dispersion tank for 30 min. After the fineness of the slurry reaches 50 μm, Component A is obtained. Step 2. Prepare Component B: Mix tetraethyl orthosilicate and absolute ethanol, and slowly add a hydrochloric acid solution to the mixture at a stirring speed of 400 r / min, and finish adding within 30 min. Continuously stir for 70 min for hydrolysis reaction, and then add absolute ethanol for dilution to obtain Formulation Component B. Step 3. Mix Component A and Component B evenly according to a mass ratio of 100:43 to obtain a heat-resistant self-healing anticorrosive coating.

[0027] Add ethanol accounting for 10% of the coating mass to the heat-resistant self-healing anticorrosive coating obtained by mixing evenly in Step 3, and spray it on a steel plate to form a dense heat-resistant shock-resistant anticorrosive zinc silicate coating.

[0028] Example 3

[0029] A heat-resistant self-healing zinc silicate anticorrosive coating in this example comprises Component A and Component B with a mass ratio of 100:43; by mass parts, Component A includes 15 parts of ethanol, 20 parts of xylene, 5 parts of a rheology aid, 44.5 parts of zinc powder, and 15.5 parts of a filler; Component B includes 45 parts of tetraethyl orthosilicate, 0.6 parts of a hydrochloric acid solution, and 54.4 parts of absolute ethanol. The filler is a composition of low-melting glass powder, zinc oxide powder, and lamellar graphene with a mass ratio of 10:20:1; the particle size of the zinc powder is 1000 mesh; the particle size of the low-melting glass powder is 4000 mesh, the low-melting glass powder is a micro-nano scale filler processed by a ball milling process twice, the particle size of the zinc oxide powder is 1 μm; the diameter of the lamellar graphene powder is 10 μm; the tetraethyl orthosilicate is a tetraethyl orthosilicate polymer with a molecular weight of 40%; the concentration of the hydrochloric acid solution is 0.5 mol / L; the rheology aid is fumed silica, organic bentonite, and polyvinyl butyral.

[0030] Its specific preparation method is as follows: Step 1. Prepare Component A: Add a dispersion aid sodium dodecyl sulfonate to an ethanol solution, with an addition amount of 5% of the mass of graphene, ultrasonically disperse for 10 min and mix with xylene, add a rheology aid under stirring, add a filler after uniform dispersion, transfer to a sand mill for grinding after stirring for 10 min, and transfer the ground slurry to a dispersion tank after grinding; slowly add zinc powder, and disperse and mix on the dispersion tank for 30 min. After the fineness of the slurry reaches 50 μm, Component A is obtained. Step 2. Prepare Component B: Mix tetraethyl orthosilicate and absolute ethanol, and slowly add hydrochloric acid solution to the mixture at a stirring speed of 300 r / min, and finish adding within 20 min. Continuously stir for 50 min for hydrolysis reaction, and then add absolute ethanol for dilution to obtain Component B of the formulation. Step 3. Mix Component A and Component B evenly according to a mass ratio of 100:43 to obtain a heat-resistant self-healing anti-corrosion coating.

[0031] Add 10% ethanol by the mass of the coating to the heat-resistant self-healing anti-corrosion coating obtained by mixing evenly in Step 3, and then spray it on the steel plate to form a dense heat-resistant shock anti-corrosion inorganic zinc silicate coating.

[0032] The comparative example is the shop primer described in the specific embodiment of the patent application with the application number 202311527604.7, the application date of November 16, 2023, the publication number CN117736592A, and the title "A Preparation Method of Ablation-Resistant Shop Primer".

[0033] Perform performance tests on the shop primers obtained in Examples 1-3 and the shop primer of the comparative example, and the results are shown in Table 1: Table 1 Performance Test Results of Examples and Comparative Examples

[0034] It can be seen from Table 1 that the adhesion of the coatings of the present invention after thermal shock at 600 °C is greater than 3 Mpa, indicating that the coatings of the present invention have good thermal shock resistance. The open circuit potential (OCP) is an important indicator to test the cathodic protection ability of the coating. The longer the time that the sample is immersed in 3.5% sodium chloride solution and is lower than -0.86 V, the longer the time that the coating provides cathodic protection for the substrate, indicating that the rust prevention and self-healing performance of the coating is better. The above examples show that the coatings of the present invention have good thermal shock and anti-corrosion properties.

[0035] Schematic diagram of the structural change of the modified coating and the traditional coating at 600 °C is as Figure 1As shown. In the traditional coating, inert conductive fillers are added to replace part of the zinc powder in the filler. However, at 600 °C, these conductive fillers will undergo severe oxidation, generating oxides at the interface between the filler and the coating, and thus significantly reducing the bonding strength of the coating. The melting of zinc powder also generates a large number of voids in the coating, ultimately significantly reducing the shielding function and cathodic protection of the coating. Due to the addition of small-sized low-melting glass powder in the modified coating, while significantly improving the coating bonding strength, only small-sized in-situ pores are left, and the lamellar fillers also inhibit the corrosion of oxygen into the interior of the coating. Due to the combined action of the lamellar fillers and the low-melting glass powder, the pore defects of the coating at high temperature are reduced, so the zinc powder does not undergo significant melting migration and most of it remains restricted in situ. Therefore, the coating still has cathodic protection function and a certain shielding effect after thermal shock. The cross-section BSE of the modified coating in Example 3 after thermal shock and after immersion in 3.5% salt water solution for 168 hours is as Figure 2 shown. The coating has an environmentally responsive protection structure, and the environmentally responsive protection structure includes a secondary film-forming - microporous structure of the coating after thermal shock in a high-temperature environment and a self-healing dense structure in a normal-temperature corrosion environment. Due to the self-healing function of the coating, the coating becomes relatively dense after being corroded by the salt water solution, and no obvious corrosion reaction layer appears at the coating matrix interface.

Claims

1. A heat-resistant self-repairing zinc silicate anticorrosion coating, characterized in that: The coating comprises a component A and a component B in a mass ratio of 100:43; in terms of mass fractions, the component A comprises 15 parts of ethanol, 20 parts of xylene, 5 parts of a rheological additive, 40-45 parts of zinc powder and 15-20 parts of a filler; the component B comprises 35-45 parts of ethyl orthosilicate, 0.3-0.6 parts of a hydrochloric acid solution and 54.4-64.7 parts of anhydrous ethanol; the coating has an environmentally responsive protective structure; The filler is a combination of two or more of low-melting-point glass powder, zinc oxide powder, conductive mica powder, and flaky graphene powder; The environmentally responsive protective structure includes a secondary film-forming microporous structure of the coating in a high-temperature environment and a self-repairing dense structure in a normal-temperature corrosion environment.

2. A heat-resistant self-repairing zinc silicate anticorrosive coating according to claim 1, characterized in that: The particle size of the zinc powder is 2000-800 meshes, the particle size of the low-melting-point glass powder is 5000-3000 meshes, the particle size of the zinc oxide powder is 500nm-1μm, the particle size of the conductive mica is 1250 meshes, and the diameter of the flaky graphene powder is 10μm.

3. The heat-resistant self-repairing zinc silicate anticorrosive coating according to claim 1, characterized in that: The low melting point glass powder is a micro-nano scale filler that is secondary processed by a ball milling process.

4. The heat-resistant self-repairing zinc silicate anticorrosive coating according to claim 1, characterized in that: The concentration of the hydrochloric acid solution is 0.3-1 mol / L, and the tetraethyl orthosilicate is a 40% molecular weight ethyl silicate polymer.

5. The heat-resistant self-repairing anti-corrosion coating according to claim 1, characterized in that: The rheological additive is selected from one or a mixture of fumed silica, organic bentonite and polyvinyl butyral.

6. A method for preparing the heat-resistant self-repairing zinc silicate anticorrosive coating according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1, preparing component A: ethanol and xylene are mixed, rheological additive is added under stirring, filler is added after uniform dispersion, stirring for 10-20 minutes, and then the mixture is transferred to a sand mill for grinding. After grinding, the ground slurry is transferred to a dispersion tank; zinc powder is slowly added, and dispersed and mixed in the dispersion tank for 30 minutes. When the slurry fineness reaches 50 μm, component A is obtained; Step 2, preparing component B: mix tetraethyl orthosilicate and anhydrous ethanol, and slowly add hydrochloric acid solution to the mixture at a stirring speed of 300-400 r / min, and complete the addition within 20-30 minutes, continue stirring for 50-70 minutes to perform a hydrolysis reaction, and then add anhydrous ethanol to dilute to obtain component B of the formula; Step 3: Evenly mix component A and component B in a mass ratio of 100:43 to obtain a heat-resistant self-repairing anti-corrosion coating.

7. The method for preparing the heat-resistant self-repairing zinc silicate anticorrosive coating according to claim 6, characterized in that: When adding filler in step 1, if the added filler is flake graphene, a dispersing aid sodium dodecyl sulfate needs to be added to the ethanol solution, the added amount is 5% of the mass of the graphene, and ultrasonic dispersion is performed for 10 minutes.

8. The method for preparing the heat-resistant self-repairing zinc silicate anticorrosive coating according to claim 6, characterized in that: When adding filler in step 1, if the added filler is conductive mica powder, the conductive mica powder needs to be surface-modified with a titanate coupling agent, diluted with a solvent, stirred, ultrasonicated, filtered, and dried before use.

9. The method for preparing the heat-resistant self-repairing zinc silicate anticorrosive coating according to claim 6, characterized in that: Step 3: The heat-resistant self-repairing anti-corrosion coating obtained by mixing evenly is diluted with 0-10% ethanol by weight of the coating and then sprayed on the steel plate to form a dense heat-resistant self-repairing zinc silicate anti-corrosion coating.

10. The method for preparing the heat-resistant self-repairing zinc silicate anticorrosive coating according to claim 9, characterized in that: The heat shock resistant and corrosion resistant inorganic zinc silicate coating has cathodic protection characteristics before and after the thermal shock, and has the function of self-repairing coating defects. After the thermal shock, the cohesion of the coating and the coating-substrate bonding strength will be improved, and the formed microporous coating structure will improve the cathodic protection effect of the coating. Subsequently, the micropores of the coating will be self-repaired under the action of cathodic protection to densify the coating.

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